docs: add OpenIAP compliant badge to README

Author: hyochan

README.md

@@ -3,7 +3,7 @@
 <div align="center">
   <img src="https://hyochan.github.io/expo-iap/img/icon.png" alt="Expo IAP Logo" width="150" />
 
-  [![Version](http://img.shields.io/npm/v/expo-iap.svg?style=flat-square)](https://npmjs.org/package/expo-iap) [![Download](http://img.shields.io/npm/dm/expo-iap.svg?style=flat-square)](https://npmjs.org/package/expo-iap) [![CI](https://github.com/hyochan/expo-iap/actions/workflows/ci.yml/badge.svg)](https://github.com/hyochan/expo-iap/actions/workflows/ci.yml) [![codecov](https://codecov.io/gh/hyochan/expo-iap/graph/badge.svg?token=47VMTY5NyM)](https://codecov.io/gh/hyochan/expo-iap) [![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fhyochan%2Fexpo-iap.svg?type=shield&issueType=license)](https://app.fossa.com/projects/git%2Bgithub.com%2Fhyochan%2Fexpo-iap?ref=badge_shield&issueType=license)
+  [![Version](http://img.shields.io/npm/v/expo-iap.svg?style=flat-square)](https://npmjs.org/package/expo-iap) [![Download](http://img.shields.io/npm/dm/expo-iap.svg?style=flat-square)](https://npmjs.org/package/expo-iap) [![OpenIAP](https://img.shields.io/badge/OpenIAP-Compliant-green?style=flat-square)](https://openiap.dev) [![CI](https://github.com/hyochan/expo-iap/actions/workflows/ci.yml/badge.svg)](https://github.com/hyochan/expo-iap/actions/workflows/ci.yml) [![codecov](https://codecov.io/gh/hyochan/expo-iap/graph/badge.svg?token=47VMTY5NyM)](https://codecov.io/gh/hyochan/expo-iap) [![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fhyochan%2Fexpo-iap.svg?type=shield&issueType=license)](https://app.fossa.com/projects/git%2Bgithub.com%2Fhyochan%2Fexpo-iap?ref=badge_shield&issueType=license)
 
 Expo IAP is a powerful in-app purchase solution for Expo and React Native applications that conforms to the Open IAP specification. It provides a unified API for handling in-app purchases across iOS and Android platforms with comprehensive error handling and modern TypeScript support.